Here is Hollingers take on him:
+ Passive combo forward with good midrange shot. Excellent finisher in transition.
+ Long-armed wing defender who needs to add strength. Can play 4 in a pinch.
+ Decent lateral movement; solid defender who often guards opponent's best wing.
Williams is a perfectly decent small forward, which would be totally fine if he hadn't been the second overall pick and then got a five-year, $35 million contract when his rookie deal expired. Compared to those expectations, he's been a disappointment. His lack of improvement over the past three seasons has been particularly deflating; despite a sign here and a flash there, his production hasn't budged an inch.
The best thing going for Williams is his midrange jumper -- he made 43.7 percent of his long 2s last season. However, he's been unable to extend his range to the 3-point line, which would make a huge difference for him in efficiency. Although Williams doesn't look for his offense, his size and athleticism often force opposing wings to foul him; he averaged 0.32 free throw attempts per field goal attempt without being terribly aggressive or tricky. Again, this tantalizes, but no turning of the corner appears in the offing.
Defensively, it's a similar story. Williams is a good, solid 3 with outstanding length and reasonable mobility, but he's not a guy who eats nails for breakfast. You don't want to match him up against top-notch scorers every night, although the Hawks often were forced to.
Basically, this is what he is. He's 25 and he hasn't progressed in three years. He'll have a nice career as a sometime starter at the 3, but I think we can stop projecting beyond that.